The Castellvi classification is used to classify lumbosacral transitional anomalies and was published by Castellvi et al. in 1984 [^1].
Classification
Castellvi type | Designation | Description |
Type Ia | Unilateral dysplastic Processus transversus | This type represents a unilaterally prominent, triangular-shaped transverse process with a width of at least 19 mm. |
Type Ib | Bilateral dysplastic transverse process | This type represents a bilaterally prominent, triangular-shaped transverse process with a width of at least 19 mm. |
Type IIa | Unilateral incomplete lumbarization\/sacralization | In this type, a prominent transverse process is present unilaterally and follows the contour of the ala ossis sacri. This type is considered incomplete because a diarthrodial joint appears to exist between the sacrum and the transverse process. |
Type IIb | Bilateral incomplete lumbarization\/sacralization | In this type, a prominent transverse process is present bilaterally and follows the contour of the ala ossis sacri. This type is considered incomplete because a diarthrodial joint appears to exist between the sacrum and the transverse process. |
Type IIIa | Unilateral complete lumbarization\/sacralization | This type is similar to Type II, except that no diarthrodial joint exists between the sacrum and the transverse process; instead, unilateral ossification has occurred. |
Type IIIb | Bilateral complete lumbarization\/sacralization | This type is similar to Type II, except that no diarthrodial joint exists between the sacrum and the transverse process; instead, bilateral ossification has occurred. |
Type IV | Mixed | Patients with this type exhibit a Type II anomaly on one side and a Type III anomaly on the other side. |
